FIG. 6 shows a conventional split-type vulcanizing mold although not disclosed in Patent Document. As shown in FIG. 6, a lower side mold 2 is fixed on the top of a lower platen 1, and a molding recess 2A is formed on the top surface of the lower side mold 2. An upper platen 3 is provided above the lower platen 1, and an upper side mold 4 is fixed to the underside surface of the upper platen 3 with a plurality of bolts (not shown). Further, a molding recess 4A is formed on the underside surface of the upper side mold 4. A cylinder (not shown) in vertical posture is provided above the upper platen 3, and an operation of the cylinder causes the upper platen 3 to move vertically to cause the upper side mold 4 to approach and part from the lower side mold 2. A segment mold ring 5 ring-like in shape as a whole is disposed radially outer sides of the upper side mold 4 and the lower side mold 2. The segment mold ring 5 comprises sector molds 6 arc-like in shape divided in, for example, 9 pieces in the circumferential direction thereof, and sector segments 7 divided similarly in 9 pieces in the circumferential direction thereof, fixed to the radially outer sides of the respective sector molds 6, and a molding recess 6A is formed on the inner surfaces of the respective sector molds 6. The top surfaces of the respective sector segments 7 are movably supported by the underside surface of the upper platen 3, extending radially outer side of the upper side mold 4.
When the respective sector segments 7 are moved radially inwardly, and the respective sector molds 6 integral with the respective sector segments 7 come to be in close contact with the respective peripheries of the upper side mold 4 and the lower side mold 2, a vulcanization space where a tire is housed to be vulcanized is formed by the sector molds 6, the upper side mold 4, and the lower side mold 2.
An outer ring 8 annular in shape, surrounding the sector segments 7 is disposed on the radially outer side of the sector segments 7, and the upper end of the outer ring 8 is fixed to the underside of an outer end of a bolster plate 9 of a vulcanizer with a bolt 11, and with a spacer ring 10 interposed therebetween. The spacer ring 10 is fixed to the top surface 8C of the outer ring 8 with a bolt 12. The bolster plate 9 is moved vertically by an elevating mechanism (not shown) to thereby cause the outer ring 8 to move in the axial directions thereof, as shown by the arrows A and B. A sloping face 8A inwardly sloping from the bottom to the top is formed on the inner periphery of the outer ring 8. A sloping face 7A identical in gradient to the sloping face 8A of the outer ring 8 is formed on the outer peripheries of the respective sector segments 7, and the sloping face 7A and the sloping face 8A are linked together with dovetail groove joints so as to be slidably engaged with each other.
Accordingly, upon the outer ring 8 moving vertically relative to the upper platen 3, the respective sector segments 7 are moved radially inwardly or outwardly, by a wedging action of the sloping faces 7A and the sloping face 8A, in synchronization with each other while being guided by the upper platen 3. A green tire is housed in the vulcanization space to be vulcanized by causing a vulcanizing medium at a high temperature and high pressure to act thereon.
In order to prevent occurrence of gaps among the upper side mold 4, the lower side mold 2, and the respective sector molds 6 due to an internal pressure of the vulcanizing medium, thereby creating a cause for spewing of rubber, the upper platen 3 and the bolster plate 9 are pushed down in the direction of the arrow A (downward in the axial direction) with a predetermined force during vulcanization, thereby causing a predetermined clamping force to act on the upper side mold 4, the lower side mold 2, and the respective sector molds 6.
With the conventional split-type vulcanizing mold shown in FIG. 6, if, for example, the kind of tire to be produced is changed, there occurs the need for reassembling the mold into another mold. As described hereinbefore, the mold is made up by stacking the respective sector molds 6 and the respective sector segments 7 radially outwardly of the upper side mold 4 and the lower side mold 2, so, even if the respective sector molds 6 and the respective sector segments 7 are fabricated within predetermined dimensional tolerances in the radial direction, there occurs variation in dimensions in the radial direction, due to piling-up of the dimensional tolerances. Also, respective dimensions of the sector segments 7 and the outer ring 8 in the axial direction thereof, as well as the sloping face 7A and the sloping face 8A have fabrication tolerances. Accordingly, there occurs insufficiency in a clamping force of the outer ring 8, acting on the respective sector molds 6, thereby creating a cause for spewing of rubber.
With the conventional split-type vulcanizing mold, as a countermeasure for preventing the spewing of tire rubber, a shim 13 with an appropriate thickness is sandwiched between the underside surface 9A of the bolster plate 9 and the top surface 10A of the spacer ring 10, (hereinafter referred to as shim adjustment), to be tightened up with a bolt 11, as shown in FIG. 7, thereby absorbing the dimensional errors of the mold and so forth, by adjusting an extensional dimension of the outer ring 8 from the underside surface 9A of the bolster plate 9, so as to prevent insufficiency in the clamping force.
Further, in order to prevent the spewing of rubber as a result of the molding recesses of the respective sector molds coming into contact with a tire prior to the respective sector molds coming to be in close contact with the respective peripheries of the upper side mold and the lower side mold, causing rubber of the tire to flow into gaps of tight-contact parts, there has been developed a tire vulcanizing mold die (Patent Document 1: refer to JP 2000-102927 A) wherein there are disposed movable pieces used for blocking the gaps of the tight-contact parts prior to the respective sector molds coming to be in close contact with the respective peripheries of the upper side mold and the lower side mold.
With the conventional mold for executing the shim adjustment described as above, since the shim adjustment is made after occurrence of the spewing of rubber of a tire, problems have been encountered in that there occur the needs for reworking due to poor appearance of the tire with the spewing of rubber occurring thereto, stopping production in a vulcanization process until completion of the shim adjustment, increasing the number of process steps for making the shim adjustment, and so forth.
Further with the tire vulcanizing mold die as disclosed in Patent Document 1, the spewing of rubber of a tire in the middle of the step of clamping the mold can be prevented, however, as it is impossible to eliminate conditions of insufficiency in a camping force of the mold, a problem has been unavoidable in that rise in internal pressure of the vulcanizing medium during vulcanization causes butting parts of the sector molds to open up, resulting in occurrence of the spewing of the rubber out of the butting parts.
In view of those problems, the invention has been developed, and it is a first object of the invention to obtain an proper clamping force of a mold without the need for the shim adjustment.
It is a second object of the invention to cause an outer ring to move smoothly accompanying movement of a bolster plate.